Stabilization of polyisobutylene polymers with sulfur and benzotriazoles



United States Patent 3,239,483 STABILIZATION ()F POLYISOBUTYLENE POLY MERS WITH SULFUR AND BENZOTRIAZOLES John J. Higgins, Roselle, N.J., assignor .toEsso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Aug. 8, 1960,'Ser. No.-47,913-

1 Claim. (Cl. 26045.8)

The.present invention is concerned with the stabilization, of relative saturated polymers containing amajor proportion of C to C isoolefinsagainst attack from ultraviolet rays. More specifically, it relates to the stabilization of polyisobutylene polymers from degradation due -to attack by ultraviolet light.

'Homopolymers of C toC isoolefins, e.g., polyisobutylene,.polyisoamylene, etc. have found. increasing use in iridustry,'e.g., adhesives, tire components, electrical insulation, etc. For example, polyisobutylene polymers range from soft gums to tough elastic solids depending upon, their. viscosity average molecular weight which may range from 30,000 to over 10,000,000 (Staudinger mo lecular weights of 8,000. to 350,000). They have a nearly saturatedstructure. Such polymers are produced by a low temperature Friedel-Crafts reaction in a low freezing solvent such as methyl or ethyl chloride or carbon disulfide. Temperatures applied may range from -20 C. to 150 C. or lower. A detailed description of polyisobutylene-polymers and their preparation may be had by referring to U.S..Patents 2,248,071 and 2,856,392.

It has been found. that such polymers tend to become tacky, lose strength and. molecular weight, and degrade fairly rapidly uponexposure to the ultraviolet rays of sun light, Obviously such behavior detracts from the usefulness of these polymers.

It has now been found that polymers of C to C isoolefins, particularly polyisobutylene, may have their stability towards ultraviolet light greatly enhanced by incorporating therein a minor proportion of sulfur, .e.g.,

preferred to incorporatea minor proportion, e.g. 0.05 tov 10, preferably 0.1 to weight percent, based on polymer of a combination of both sulfur and a hydroxy phenyl benzotriazole derivative. The combination of these two materials in the polymer offers a synergistic effect in that the combination of both materials imparts a much higher degree of resistance to ultraviolet light than is secured by employing equivalent amounts of either material alone. In general, the weight ratio of sulfur to hydroxy phenyl benzotriazole derivative will vary from about 5 to 0.02. Approximately equal concentrations are, however, preferred.

The hydroxy phenyl benzotriazole derivative employed in the practice of the present invention may be denoted by the following generic structural formula:

wherein R and R are hydrocarbon radicals selected from the group consisting of C to C alkyls and C to C alkoxy groups, hydrogen, halogen, hydroxy, carboxy, amino, nitrogen or aryl groups, and n and m are integers in the range of l to 4, the sum of n and m being Patented Mar. 8, 1966 greater than 2. Particularly desired are compounds wherein at least one R group is methyl or hydrogen.

Examples thereof are:

2-(2-hydroxy phenyl)-benzotriazole 2-(2-hydroxy, 3-methyl phenyl)-benzotriazole Z-(S-amino, 2-hydroxy phenyl)-benzotriazole 2-(2,4-dihydroxy phenyl)-benzotriazole 2-(3,5-dibromo, 2,4-dihydroxy phenyl)-benzotriazole 2+(3,5 -dinitro, 2,4-dihydroxy phenyl)-benzotriazole- 2-v(2,3,4-trihydroxy, 6-carboxy phenyl)-benzotriazole 5 amino-2- (2-hydroxy phenyl benzotriazole 2-(2-hydroxy naphthyl)-benzotriazole It is noted that it has previously been suggested to employ sulfur as a heat stabilizer for polyisobutylene. However, there are many applications for such polymers wherein heat stabilization is of little or no importance, whereas, ultraviolet stabilization is a prime concern, e.g.,' in roof coatings and in blends with other polyolefins. These blendsusually in film form are used in heavy duty bags, protective coverings, outdoor furniture coverings, etc. Thus, one would not be led to employ sulfur in such compositions. Moreover, the preferred embodiment of employing acombination of sulfur and a hydroxy phenyl benzotriazole derivative and obtaining a synergistic result thereby is clearly distinguishable over the use of sulfur for heat stabilization.

Further, it is to be noted that homopolymers such as polyisobutylene are not vulcanized by sulfur, and thus the conventional use of sulfur as a curativedoes not anticipate the present invention.

In addition to the ultraviolet stabilizers of the present invention, various other conventional polymer additives such as process oils, pigments, fillers, low temperature plasticizer resins, waxes, etc. may be incorporated in the 1 A polyisobutylene polymer having a Staudinger molecular weight of about 89,000 was prepared at about to C. in the presence of a solution of aluminum chloride in ethyl chloride. Three samples of the resulting polymer were then compared as to ultraviolet light resistance.

Sample 1 was not subjected to exposure to ultraviolet light. Sample 2, containing no stabilizers, and sample 3, containing sulfur as indicated in Table I, were exposed to ultraviolet light. Sulfur was blended into sample 3 on a conventional rubber mill. Samples 1, 2 and 3 were sheeted off into strips between 20 and 50 mils in thickness. The strips were then exposed in an Atlas Fadeometer for 60 hours at a temperature of -130" F., procedure and apparatus as described in ASTM D-750-55T (carbon are light source).

After exposure to the ultraviolet light, the samples 3. were analyzed for molecular weight using the Staudinger method. The percent molecular weight retained as reported in Table I is a comparison of the 'molecular weight retention of samples 2 and 3 as compared to nonexposed sample 1.

Table 1 Samples Stabilizer Sulfur (parts by wt. per 100 parts of polymer)--. 0 1 Percent Molecular Weight Retained Alter Exposure Not ex- 40. 2 77. 3

posed As shown by the above data, a minor proportion of sulfur greatly increases the ability of polyisobutylene to resist ultraviolet degradation. In a similar test to that described, the' incorportion of 0.2 weight percent sulfur in a polyisobutylene polymer having an initial Staudinger molecular weight of about 82,000 gave a 78.6% molecular weight retention after exposure in an Atlas Fadeometer under the conditions described in Example 1. The non-.

stabilized polymer gave only 26.7% molecular weight retention when similarly exposed.

EXAMPLE 2 The same procedure described in Example I was employed with the same polyisobutylene polymer (Staudinger molecular weight of 89,000) except that a combination of sulfur and a hydroxy phenyl benzotriazole derivative was evalulated as an agent for ultraviolet light stabilization.

In sample 7, only the hydroxy phenyl benzotriazole derivative was incorporated into the polymer, whereas, in sample 6 both sulfur and the hydroxy phenyl. benzotriazole compoundlwere added to the polyisobutylene;

Sample 4 contained neither stabilizer. Sample 5 contained only sulfur as a stabilizer'and is the same as sample 3 of Example 1.

.The stabilizers were blended into the polyisobutylene. on a conventional rubber mill.' In each sample, the,

polymer was then sheeted olf at between to mils in thickness and strips from these sheets were exposed in an Atlas Fadeometer for hours at a temperature of -v F. as in Example 1. After exposure to the ultraviolet light, the samples were analyzed -for molceular.

weight using the Staudinger method and their molecular weight compared to that (89,000) of the unexposed polymer. It is to be noted that samples of Examples 1 and 2 were all exposed to the same conditions at the same time.

4 Table II Samples Stabilizer Sulfur, phr

Hyglroxy Phenyl Benzotriazole 1 derivative,

p tr

Percent Molecular Weight Retained After Exposure;

1 Sold under the trade name of 'Iinuvin P by Geigy Chemical Company j and having the structure 2-(2-hydroxy-5-methylphenyl)benzotriazole. It is an ofi-white crystalline powder having a melting point 0f'131-2 C. A solution of 25 mg. in 100 ml. of chloroform in a one eentimeter Beekman cell transmits practically no radiation at 380 mu yet transmits 100% at 0.0001. 'gmJlOO ml.,. Ethanol-05, Acetone-5.0, Styrene-7.0, and Hexane-Ll. V g g 1 As shown by .the above data,= although individually both sulfur andhydroxy phenyl benzotriazole aiford pro- 20 tection against ultraviolet rays, the combination of both materials (sample 6) gives a completely unexpected high degree of resistance to ultraviolet light breakdown and is considerably more eifective than the use of equivalent amounts of either sulfur or hydroxy phenylbenzotriazole 2 derivatives alone.

use of additional modifyingagentsr Having described the present invention, that which is sought to be pro-1 30 tected is set forth in the following claim. 7 What is claimed is:-

A composition comprising polyisobutyleneand between about 0.1 and about 5.0 wt. percent, based on p'olymer,

of a combination of sulfur and 2-.(2rhydroxy-5rmethyl 35 phenyl benzotriazole), wherein the weight ratio of :sulfur to said benzotriazole compound isabout 1:21.

References Cited by the Examiner UNITED, STATES PATENTS LEON J. 'BER COVITZ, Primary Examiner.

ERMAN, Examiners.

410 mu. Tinuvm P exhibits the following solubilities at,25 0.: Water- Various: modifications to. the present invention" suggest themselves to those skilled in'the art, .e.g. the.

Stiratelli 26045.8

A. RUNNINS, MILTON'STERMAN, JOSEPH R3 LIB: 

